1. Field of the Disclosure
The present disclosure relates to an illumination switch having a function to illuminate an illumination surface such as an operation surface of an operation knob by light from a light source.
2. Description of the Related Art
Japanese Examined Utility Model Registration Application Publication No. 7-1708 discloses an illumination switch provided with an illumination portion 24a in an upper surface of an operation portion that is operated with a finger or the like to be rotated. Light from a light source that is provided below the operation portion is guided through a light guide body to the illumination portion 24a. 
A configuration is disclosed in which the operation portion 31 is provided with a light guide path in which a hole 23b bored so as to penetrate in the up-down direction, and a light emission portion is disposed between projections of the operation portion 31. According to the configuration, even when an illumination area is not directly above the light source, it is possible to illuminate the illumination portion of the operation portion by using the light guide member.
In addition, Japanese Unexamined Patent Application Publication No. 2009-9790 discloses an illumination switch that includes: an operation knob having an operation surface; a first light guide member 20 that guides light emitted from a light source provided to the operation knob, to the operation surface; and a second light guide member 30 that makes the light emitted from the light source, into parallel light. In the illumination switch, parallel light R1 emitted from the second light guide member 30 is refracted from an incident surface 21 of the first light guide member 20. Light R3 after the refraction propagates through the interior of the second light guide member 30 and is reflected by a reflection surface 23 provided at a bottom portion of the second light guide member 30. Light R4 after the reflection propagates through the interior of the first light guide member 20 in a second direction D2 and reaches a light emission surface 22. In the illumination switch, the light emitted from the light source is reflected by the reflection surface 23 and then emitted, so that it is possible to direct sufficient light also to a peripheral portion of the light emission surface 22, and it is possible to prevent brightness unevenness of the light emission surface 22.
However, in the existing illumination switch described above, when the operation knob having the illumination surface rotates relative to the light source by an operation with a finger or the like, brightness (illumination) unevenness occurs in the illumination surface due to a change in the path through which the light from the light source is guided to the illumination surface.